CHEM 111 Lecture Notes - Ernest Rutherford, Cathode Ray, Plum Pudding Model
Document Summary
Element simplest type of matter that retains its physical and chemical properties, consists of only 1 type of atom. Democritus (c. 460 370 bc) proposed the existence of the smallest particle of a substance, called atoms" from atomos (gr. John dalton (1766 1844) proposed modern picture of the atom, still considered to be indivisible, each element has unique atoms. Cathode rays: j. thomson (1856 1940) worked with cathode rays (electric current) to determine their mass, calculated to be 1 / 1000 that of a hydrogen atom there must be something smaller than an atom. Ernest rutherford (1871 1937) demonstrated that the atom was mostly empty space and the existence of a small, positively charged nucleus with most of the mass. Shape spherical with a small, positive nucleus surrounded by one or more negative electrons. Takes up most of the mass (~99. 97% of the total) but takes up only a quadrillionth of the volume (1 x 10-15)
